Superman is revived at the Fortress of Solitude by his robot and then races back to Metropolis where he battles his misguided clone. He defeats his clone by having the Kryptonite cartridge from Lex's gun stuck to his clones chest with tar and uses his laser vision to bust it open, making a cloud of Kryptonite dust that his clone inhales. This coats his lungs with a lethal dose and he drops the Superman Memorial statue on himself, then dies in the real Superman's arms from the crushing wound and lungs coated with Kryptonite. The people of Metropolis see he is the real Superman ans he earns their trust back. Superman then revealed his identity as Clark Kent to Lois at her apartment, and the movie ends showing Lex Luthor is still alive and marveling at how it would seem that Superman can't be killed after all.
Quantom X ★
Chosen answer: When they call Doomsday a machine, they don't mean a literal machine. Just that he was built/designed. The comics were much the same. Doomsday was created by placing a baby on the most dangerous planet in the universe, and cloning that baby every time it died, forcing it to adapt. Doomsday eventually escaped this torture.
MasterOfAll